For service and parts needs, visit your dealer. You will receive genuine GM parts and GM-trained and supported service people.
Genuine GM parts have one of these marks:

Vehicle Care
California Proposition 65 WarningNavigation System
If the vehicle has a navigation system, there is a separate navigation manual
that includes information on the radio, audio players, and navigation system.
The navigation system provides detailed maps of most major freeways and roads.
After a destination has been set, the system provides turn-b ...
Air/Wind Noise
Special Tools
CH-39570 Chassis Ear
GE-41416 Ultrasonic Leak Detector
Warning: Refer to Assistant Driving Warning in the Preface section.
To analyze a reported windnoise condition, test drive the vehicle to
determine the origin of the noise.
Choose a regular route with smooth and strai ...
Installation Procedure
Drill 8 mm (5/16 in) for plug welding along the edges of the rear bumper
impact bar stud plate as noted from the original panel.
Note: If the location of the original plug weld holes can
not be determined, space the plug weld holes every 40 mm (1½ in).
Clean and prepare the ...